As the volatile Republican primary drags on, party operatives are growing concerned that their presidential nominee could be woefully unprepared to wage a national campaign against President Barack Obama.

Unlike the extended 2008 Democratic primary — during which Obama and Hillary Rodham Clinton built experienced, highly organized political operations — only two of the four Republicans still standing, Mitt Romney and Rep. Ron Paul (Texas), have assembled national campaigns capable of pivoting to the general election. And of the two, only the former Massachusetts governor is considered a real contender for the nomination.

Romney has been a weak frontrunner and has demonstrated vulnerabilities that could doom his bid. Most recently, he has been attempting to fight off former Sen. Rick Santorum (Pa.), who had been considered a major underdog until he became the latest alternative to surge in early February. Whether Romney can defeat Santorum in Arizona and Michigan this week could determine the fate of his campaign heading into Super Tuesday.

But veteran GOP operatives with experience assembling and running presidential campaigns worry that Santorum and former Speaker Newt Gingrich (Ga.) have thus far proved incapable of translating electoral success in the primary into a national political operation, arguing that there is insufficient time between now and Nov. 6 to construct an organization on par with Obama’s re-election machine. That will be even more true if the eventual nominee doesn’t start to build such an operation until the conclusion of a bloody primary that might not end until June.

Steve Schmidt, who managed Arizona Sen. John McCain’s 2008 presidential bid, said building an effective national campaign virtually from scratch in less than a year — much less the preferred period of at least 18 months — is difficult to impossible. Schmidt, who is also a veteran of President George W. Bush’s 2004 re-election, said the Republican nominee could be at a severe disadvantage in identifying and turning out voters against Obama, whose 2008 campaign set a new standard for organizational muscle.

“John McCain proved that you don’t need much of an organization to win a Republican primary — and you still don’t. But you need organization to win the general,” Schmidt told Roll Call, adding that Arizona’s senior Senator won the 2008 nomination “on a wing and a prayer and was never really able to recover on an organizational level against the Obama campaign.”

Gingrich and Santorum — as well as candidates who have since exited the race — seem to hope to win the nomination in much the same way as McCain did, and indeed, they have alternately thrived despite organizational limitations. Gingrich handily won South Carolina; Santorum narrowly won Iowa and was victorious in “beauty contests” in Colorado, Minnesota and Missouri.

Fundraising for Gingrich and Santorum has picked up markedly from earlier in the campaign. They did not trail Romney by much in January, raising $5.6 million and $4.5 million, respectively, to the former governor’s $6.5 million.

Gingrich and Santorum have been boosted by independently run political action committees, although the pro-Romney Restore Our Future super PAC continues to significantly outraise and outspend rivals.

But winning a general election fought on a narrowly divided Electoral College map — as polls suggest of this year’s race — requires significant resources and preparation, particularly against what is already a strong, well-funded Obama campaign. More than 300 paid staffers work from the president’s Chicago re-election headquarters; the campaign has been funded by more than 1.4 million donors — many classified as unpaid volunteers — and new field offices are opening daily.

Republican consultant Ed Rollins said a good candidate is essential to winning the White House — but is not enough. “To win, you need two elements,” Rollins said in an interview with Roll Call. “A good candidate can’t win without a good campaign structure and good operatives.”

Schmidt said a worthy model for first-time presidential candidates is Bush, who began formulating the “mechanics, plans and architecture” of his 2000 White House bid in 1998, the year he won re-election as Texas governor.

With that in mind, Schmidt labeled as “fanciful” the notion that Republicans could ramp up a campaign “overnight” and still hope to compete with Obama should they fail to produce a nominee until their Tampa convention in late August.

Both Paul and Romney ran for president in 2008 and began the 2012 race with existing campaign networks. Each is attempting to follow in the footsteps of previous Republican nominees who ran at least once and lost before winning their party’s nod — Reagan, former Senate Majority Leader Bob Dole (Kan.) and McCain among them.

Despite the advantages that often accompany a second bid, some unaffiliated GOP operatives contend that not having run for president previously is no excuse for the organizational ineptness exhibited by some of this year’s first-time candidates. That Gingrich and Santorum failed to qualify for the primary ballot in the key Super Tuesday state of Virginia — where they are both official residents — troubles them.

“The fact that there are states where they aren’t on the primary or caucus ballot has got to be a complete embarrassment,” one Republican campaign operative said.

Getting on the ballot in Virginia is “‘ABC’ easy,” added a Republican with presidential campaign experience who now works on K Street. “It is essential that the nominee have a national organization. Romney has the closest to one; Gingrich and Santorum have nothing.”

Santorum also failed to qualify to compete for the full slate of Ohio’s convention delegates, although he is on the Buckeye State’s March 6 ballot. In Indiana, there is still a chance Santorum might fail to qualify for the May 8 primary ballot. Gingrich, meanwhile, failed to qualify for the Feb. 7 Missouri primary. In 2008, first-time candidates did not appear to experience similar missteps.

The Obama campaign, unburdened by a primary, is free to focus on the general election. Already, the president has 46 field offices in six crucial battleground states that could decide the race. Among them: 11 in Iowa; three in Nevada, including two in greater Las Vegas and one in Reno; eight in New Hampshire; four in Virginia; and eight in Ohio.

And just last week, the Obama campaign opened its 12th Florida office. That one, in Tampa, is probably not the last in this vote-rich metro area that also is home to the Aug. 27&ndash;30 GOP convention. “Nine months from now, our organization will be more than ready to turn out the vote,” Obama campaign spokeswoman Katie Hogan said.

In 2008, Obama and Clinton were bolstered by similarly strong organizations as they campaigned from state to state until the Democratic primary concluded in June. In this year’s GOP contest, Romney, and to a lesser degree, Paul, have been able to pivot from state to state with operational effectiveness. However, Paul has yet to win a single state primary.

Santorum’s shortcomings were evident when he followed his strong Iowa finish with disappointing performances in the next four states. Gingrich won big in South Carolina, only to lose big to Romney in Florida 10 days later.

The Romney campaign is alone in employing a sophisticated voter turnout operation complete with absentee and early voting programs. He has received almost 2,900 endorsements, and all are described by his campaign as being actively involved.

Romney’s team has “put together a top-notch organization because they learned from 2008,” Rollins said. “It’s impressive, and I’m not usually impressed by others’ ground games. But that’s the sign of a good operation. They’ve adjusted.”

The Gingrich, Santorum and Paul campaigns did not respond to requests for comment.